Under that law, parents and guardians can use physical force, including hitting, in disciplining their children as long as it is not intended to cause "serious injury, disfigurement, extreme pain or emotional distress."

In Pierce's case, police said they initially received the allegation from the department of Children and Youth Services and investigated it.

"We do get a lot of (CYS) referrals that don't amount to anything," said Harrisburg police Lt. Terry Wealand. "Sometimes they can be misunderstandings. When we do get a case and there's something to it, we run it through the district attorney's office. We don't charge someone unless it warrants charges."

But this case that police felt was warranted fell apart at Pierce's court hearing on Jan. 4. Pierce came to the hearing armed with photos that her daughter posted on social media holding guns and piles of money to prove she was struggling with an out-of-control teen. When Pierce said she confronted her daughter about the images, her daughter threw her arms up and said, 'Get away from me.'

That additional information convinced Jack Canavan, the senior deputy prosecutor in the courtroom, to agree to reduce the charge to a summary offense of harassment. Pierce pleaded guilty and that could have been the end of it, but Judge Deborah Curcillo then asked how old Pierce's daughter was.

"Sixteen," Pierce answered. "And she's bigger than me."

The defense attorney, Curcillo and Canavan all paused and looked at each other, said Chief Deputy Sean McCormack, who handles child abuse prosecutions for the Dauphin County District Attorney's office.

Canavan then asked Curcillo if they could pull back case, so he could dismiss it. McCormack said he believed there was a self-defense component to the case in addition to the parental discipline defense.

McCormack said Pierce's case isn't the best example of how assault cases involving children should be handled since punching "generally isn't considered appropriate discipline."

But each case must be viewed with its own unique set of facts.

While Harrisburg police weren't consulted about the dismissal of Pierce's case, they said they generally haven't had problems making child abuse cases stick under Pennsylvania's law.

In his nearly two-decade career, Wealand said he was only aware of a single other case that was tossed because of the parental discipline exemption.

In that case, about 18 years ago, police charged a mother with hitting her child against the head with a 1-liter soda bottle filled with frozen water. But a magisterial district judge threw out the case, recalling harsh discipline he endured as a child.

Adults often repeat the discipline enacted upon them, McCormack said, instead of considering new information or what has been scientifically proven to be effective.

"You don't want to criminalize everything," McCormack said. "But there are times we'll see horrible photos of abuse and the parents will say, 'My parents didn't spare the rod, and look, I turned out great.'"

There can be a fine line between discipline and abuse, McCormack said.

"There needs to be a balance," McCormack said. "Pennsylvania's law is an attempt to strike that balance. But it is a challenge for us to prove some of these cases because of that."

Cumberland County District Attorney M.L. "Skip" Ebert said child abuse cases are always a question of degree and severity.

"I think the law is fine the way it is," he said. "It gives police officers plenty of discretion...Every incident is fact specific, but if there are repeated acts, there's going to be intervention by law enforcement."

A spokesman for the Pennsylvania District Attorneys Association also said they had not heard of complaints or difficulties from Pa.'s law allowing corporal punishment.

Child advocates, however, believe Pennsylvania's law could be tightened. There is a lot of room for hurt up to the "serious injury" threshold allowed under current Pennsylvania law.

"We still have far too much leeway in how kids are treated," said Palm. "We're still not in an ideal spot."

Other drawbacks of the law, Palm said, are that it includes the words "reasonable" and "serious injury," which can be debated and interpreted differently by parents, police and prosecutors.

While a broken nose may seem serious to a prosecutor, for example, would a judge agree?

Criminal child abuse cases that fall apart then aren't listed on the person's background check, which can be problematic, Palm said.

Palm said she would want to know if a parent believes punching a daughter in the face is acceptable discipline before hiring that woman as a day care provider, but that information would not turn up on a child abuse clearance check without the conviction.

A conviction also can help strengthen a case for intervention by Children and Youth Services.

While youth services and the court system were designed to function as two separate paths, with youth services using a lower threshold of evidence, the two paths have been overlapping more as of late, Palm said.

Parents have appealed and won against youth services at times by pointing out that their behavior is perfectly legal.

It is a complicated system, McCormack said, but he believes each system is focused on finding alternative solutions to convictions.

Convictions aren't the desired outcome, McCormack said: changing behavior is. So if Dauphin County can get a parent to attend counseling and classes, instead of facing a criminal charge, that is more likely to change behavior than a stint behind bars.

"The use of force upon or toward the person of another is justifiable if:

(1) The actor is the parent or guardian or other person similarly responsible for the general care and supervision of a minor or a person acting at the request of such parent, guardian or other responsible person and:

(i) the force is used for the purpose of safeguarding or promoting the welfare of the minor, including the preventing or punishment of his misconduct;

and

(ii) the force used is not designed to cause or known to create a substantial risk of causing death, serious bodily injury, disfigurement, extreme pain or mental distress or gross degradation."